Synthetic hydrocarbon lubricant compositions

ABSTRACT

COMPOSITIONS COMPRISING MIXTURES OF DI-N-ALKARYLS (E.G., DI-N-AKYLBENZENES) AND LINEAR MONO-OLEFIN OLIGOMERS HAVE CERTAIN IMPROVED PROPERTIES OVER THAT OF EITHER ALONE FOR EXAMPLE, MIXTURES OF THE TWO MATERIALS HAVE A LOWER --40*F. VISCOSITY, AS COMPARED TO THE INTERPOLATED VISCOSITY, THAN EITHER MATERIAL ALONE. ALSO MIXTURES OF THE TWO MATERIALS ARE MORE COMPATIBLE TO ADDITIVE COMBINATIONS THAN THE LINEAR MONO-OLEFIN OLIGOMER ALONE. STILL FURTHER, COMPOSITIONS COMPRISING THE MIXTURES AND VARIOUS ADDITIVE COMBINATIONS HAVE IMPROVED VISCOSITY INDEXES AS COMPARED TO EITHER MATERIAL CONTAINING THE ADDITIVE PACKAGE.

United States Patent O 3,808,134 SYNTHETIC HYDROCARBON LUBRICANTCOMPOSITIONS Hugh Ernest Romine, Ponca City, Okla., assignor toContinental Oil Company, Ponca City, Okla. No Drawing. Filed Aug. 9,1972, Ser. No. 280,059 Int. Cl. Cm 1/28 US. Cl. 252-59 11 ClaimsABSTRACT OF THE DISCLOSURE Compositions comprising mixtures ofdi-n-alkaryls (e.g., di-n-alkylbenzenes) and linear mono-olefinoligomers have certain improved properties over that of either alone.For example, mixtures of the two materials have a lower -40 F.viscosity, as compared to the interpolated viscosity, than eithermaterial alone. Also, mixtures of the two materials are more compatibleto additive combinations than the linear mono-olefin oligomer alone.Still further, compositions comprising the mixtures and various additivecombinations have improved viscosity indexes as compared to eithermaterial containing the additive package.

BACKGROUND OF THE INVENTION Field of the invention This invention isdirected to lubricating fluids suitable for use under extremely lowtemperature (i.e., 40 to 75 F.) conditions. The invention is directedspecifically to synthetic hydrocarbon compositions, and to mixtures ofsuch compositions, having the requisite physical properties for suchuse.

GENERAL BACKGROUND It is known that certain dialkylbenzenes (e.g., thosehaving C -C alkyl groups) have physical properties which render themuseful as low temperature lubricants. For example, US. Pat. No.3,173,965 contains such teachings. It is also known that synthetichydrocarbon lubricants which contain a major amount ofdi-n-alkylbenzenes, or di-n-long-chain alkaryls, and a minor amount ofother hydrocarbon (e.g., diphenylalkanes or trialkyl substitutedtetrahydronaphthalenes) have properties which render them useful as lowtemperature lubricants. US. Pat. Nos. 3,288,716; 3,588,739; and3,662,012 contain such teachings.

The use of linear mono-olefin oligomers as lubricants is also wellknown. While these materials have outstanding physical properties (e.g.,viscosity index and pour point) they are deficient in oxidationstability and compatibility with various conventional lubricating oiladditives.

I have discovered that mixtures of di-n-long-chain alkaryls (orsynthetic hydrocarbon compositions containing a major amount ofdi-n-long-chain alkaryls) and linear mono-olefin oligomers have certainunexpectedly improved properties over either alone.

More specifically, the mixtures of dialkaryls and linear mono-olefinoligomers provide the following improvements:

(a) The 40 F. viscosity, as compared to the interpolated viscosity, islower than that of either material alone;

(b) The mixture is more compatible to additive combinations than thelinear mono-olefin oligomers alone;

(c) Compositions comprising the mixture and various additivecombinations have improved viscosity indexes as compared to either thedialkaryls or linear mono-olefin oligomers containing the additivepackage.

PRIOR ART A search of the prior art did not produce any reference3,808,134 Patented Apr. 30, 1974 showing any advantages of mixtures ofdi-n-long-chain alkaryls and linear mono-olefin oligomers compared toeither material alone. The search did produce thirteen US. patentsconcerned with the general state of the art of the individual materials.In order to make my disclosure complete these patents were thefollowing: 2,190,918; 2,534,095; 3,173,965; 3,518,321; 2,327,705;2,746,925; 3,436,349; 2,500,165; 3,057,801; 3,449,249; 2,500,244;3,163,705; and 3,848,857.

BRIEF SUMMARY OF THE INVENTION Broadly stated, the present invention isdirected to lubricant compositions comprising mixtures of di-n-longchainalkaryls and linear mono-olefin oligomers.

In one aspect, the invention is directed to lubricant compositionscomprising mixtures of linear mono-olefin oligomers and a synthetichydrocarbon composition containing a major amount of di-n-long-chainalkaryls.

In another aspect, the invention is directed to lubricant compositionscomprising a major amount of a mixture of linear mono-olefin oligomersand di-n-long-chain alkaryls and a minor amount of conventionallubricating oil additives.

The relative amounts and nature of the various materials will bedescribed in the detailed description.

DETAILED DESCRIPTION One component of the composition of my invention isa di-n-long-chain alkaryl or a synthetic hydrocarbon compositioncontaining a major amount of di-n-long-chain alkaryls.

The term di-n-long-chain alkaryl refers to materials represented by theformula wherein R and R are alkyl groups containing from 6 to 18 carbonatoms, more suitably from about 9 to about 15 carbon atoms,and'preferably from about 10 to about 14 carbon atoms, with the sum of Rand R being from about 20 to about 28 carbon atoms and wherein A and Aare hydrogen or a C or C alkyl group, but preferably are hydrogen.

Thus the preferred di-n-long-chain alkaryl is a di-nalkylbenzene whereinthe alkyl group contains from about 10 to about 14 carbon atoms.

The alkyl groups are substantially straight-chain (thus the termn-alkaryls) wherein, preferably, at least 95 percent of the alkylsubstituents are bonded to the benzene nucleus through a secondarycarbon atom of the respective alkyl groups. While we prefer the termnalkaryls other terms such as linear alkaryls or straight chain alkarylsare equally descriptive.

The first component of my invention also includes synthetic hydrocarboncompositions containing a major amount (i.e., 60 to weight percent) ofthe di-n-alkaryls, as defined in the foregoing, and a minor amount ofother hydrocarbons, such as diphenylalkanes and trialkybsubstitutedtetrahydronaphthalenes, having molecular weights corresponding to thedi-n-long-chain alkaryls.

A particularly suitable material for the first component is a synthetichydrocarbon composition having the fol lowing composition.

Component: Percent by weight Di-n-long-chain alkaryls 61-92Trialkyl-substituted tetrahydronaphthalenes 5-30 Miscellaneous alkylaromatics:

Less than 15 Preferably less than 10 The composition is alsocharacterized as having the following properties:

Viscosity index 80-116 Pour point, F. -40-80 Molecular weight range350-526 Preferably 375-480 The di-n-long-chain alkaryls meet thedescription provided in the foregoing.

The trialkyl-substituted tetrahydronaphthalenes can be represented bythe formula wherein R and R contain from 1 to about 13 carbon atomseach, with the sum of R and R being from about 6 to about 14 and R and Rcontain from 1 to about 16 carbon atoms with the sum of R and R beingfrom about 9 to about 17. The alkyl groups, R R R and R arestraight-chain.

The trialkyl-substituted tetrahydronaphthalenes have the same boilingrange as the di-n-alkylbenzenes. In addition, they have approximatelythe same molecular weight.

This particular synthetic hydrocarbon alkaryl lubricant can be preparedby any of several methods. It can be prepared by alkylating benzene andtetrahydronaphthalene and blending the resulting product. Also, it canbe prepared by alkylating a mixture of mono-n-alkylbenzenes anddialkyl-substituted tetrahydronaphthalenes with a suitable alkylatingagent. A particularly suitable method of preparing the synthetichydrocarbon alkaryl lubricant is by the disproportionation of amonon-alkyl-benzene-rich feedstock using HF-BF aluminum bromide oraluminum chloride as the catalyst.

Suitable mono-n-alkylbenzenes are those containing from about 6 to about18 carbon atoms in the alkyl groups. Preferably, the alkyl groups of themono-n-alkylbenzenes contain from about 10 to about 15 carbon atoms. Theterm n-alkylbenzenes has been defined in the foregoing.

A particularly suitable method of preparing this latterdescribedsynthetic hydrocarbon lubricant composition is described in US. Pat. No.3,662,012.

The second component of my invention is a linear mono-olefin oligomer ormixture thereof. These materials are usually prepared from m-olefinsusing a suitable catalyst and are usually referred to as a-olefinoligomers. For preparing the a-olefin oligomers, there is used one ormore a-olefins containing from 6 to 16 carbon atoms, more suitably from8 to 12 carbon atoms and preferably 10 carbon atoms. The linearmono-olefin oligomer is characterized as containing at least 50 weightpercent, more usually at least 60 weight percent, of materialscontaining 24 to 60 carbon atoms. When the linear monoolefin oligomer isprepared by oligomerization of a-olefins containing 8 to 12 carbon atomspreferably the maximum amount of dimer present is 10 weight percent. Thelinear mono-olefin oligomers can obtain very small amounts \(usuallyless than weight percent) of branched-chainolefins or di-olefins.

If desired, in order to improve the oxidation stability thereof, thelinear mono-olefin oligomers can be treated by any of several knownmethods, such as hydrogenation or heat treatment. Whether or not thelinear monoolefin oligomers have been treated to improve their oxidationstability does not affect the improvements due to mixtures of linearmono-olefin oligomers and di-n-alkylbenzenes as described herein.

The mixtures forming the composition of my invention can contain fromabout to about 90 weight percent, more suitably from about 30 to about85 weight percent,

and preferably from about 50 to about weight percent linear mono-olefinoligomers.

USES FOR IMPROVED LUBRICANT COM- POSITIONS OF MY INVENTION As is readilyapparent to those skilled in the art, there are many uses for thelubricant compositions of my invention. They can be used as crankcaselubricants, turbojet aircraft lubricants, turbine lubricants, hydraulicfluids, transmission fluids, combination crankcase and transmissionfluids, steering fluids, and instrument lubricants.

While the lubricants of my invention have many uses per se, usually theyare used in compounded formulations containing various additives.Examples of additives which can be used include dispersants anddetergents, oxidation inhibitors, corrosion inhibitors, viscosity indeximprovers, antirust agents, and antifoam agents.

In order to disclose the nature of the present invention still moreclearly, the following examples, both illustrative and comparative, willbe given. It is to be understood that the invention is not to be limitedto the specific conditions or details .set forth in these examplesexcept insofar as such limitaitons are specified in the appended claims.

In the examples the test methods were ASTM or other standard tests. Theviscosity index was based on measured and 210 F. viscosities.

The percent deviation from interpolated --40 F. viscosity can beexplained as follows:

It is common practice in the petroleum industry to use what is known asASTM viscosity blending paper to interpolate blend viscosities fromcomponent viscosities. It is generally observed that at a giventemperature lubricant blends obey the relationship ln ln (K +A) ==X lnln (K +A)-|-(1-X) ln ln (K -l-A) where K is the kinematic viscosity ofthe blend in centistokes, K and K are the blend component viscosities, Ais approximately 0.6, and X is the weight fraction of component one inthe blend. This expression is derived from the Walther equation whichdescribes the viscosity-temperature relationship of lubricant blends.ASTM viscosity blending .paper as cited above linearly relates blendcomposition (X) to ln ln (K -l-A). This relationship was used to arriveat an interpolated blend viscosity. The difference between theinterpolated and measured blend viscosities divided by the interpolatedvalue is the percent deviation as used herein.

EXAMPLE 1 Oligomer The synthetic hydrocarbon lubricant was prepared bydisproportionation of a predominantly Cm-Cm mono-nalkylbenzene usingAlCl as the catalyst. It had the following composition by massspectrometer:

Vol. percent Di-n-alkylbenzenes 2 68 Trialkyl-substitutedtetrahydronaphthalenes 3 22.8

1 Substantially same as weight percent.

Predominantly (Biz-C14 alkyl groups.

a Substantially the same molecular Weight as the dl-ualkylbenzenes.

The physical properties of the a-olefin oligomers (a-O-O), the synthetichydrocarbon lubricant (S.H.L.)

and various mixtures of the two materials are shown in Table I below.

TABLE I Composition No.

A B C D S.H.L., percent wt 100 0 90 80 a-O-O, percent wt 0 100 20Viscosity cs. at-

F 9,587 6,769 8, 823 8,079 100 F-.- 29.77 31. 95 28. 97 28.45 210 F 5.07 5. 84 5.09 5. 12 Percent deviation from interpolated 40 4.3 9. 0Viscosity index 116 118 Pour point, F 70 60 1 Below 75.

EXAMPLE 2 This example illustrates the improvement in 40" F. viscosityof mixtures of a di-C -alkylbenzenes and two hydrogenated a-olefinollgomers prepared from decene-l.

Vol. percent 1 Di-n-alkylbenzenes 69.3 Trialkyl-substitutedtetrahydronaphthalenes 3 22.3

1 Substantially same as weight percent. Predominantly C12-Cu alkylgroups.

Substantially the same molecular weight as the di-nalkylbenzenes.

The viscosity properties of the a-olefin oligomer (a-O-O), the synthetichydrocarbon lubricant (S.H.L.) and various mixtures of the two materialsare shown in the table below.

TABLE III Percent devia- Viscosity Weight percent 210 100 0 tion index5. 92-5. 89 35. 90-35. 06 882-884 8, 2128365 119-121 4. 97-4. 98 29.03-28. 60 866-858 8, 793-8, 941 105-109 5. 15 29. 04 856 8, 559 1. 8 1175. 39 30. 40 853 8, 3. 3 123 5. 63-565 31 8131.48 886-854 8, 217-8,2542.3 128-132 5. 67 31. 92 856 8, 2 --1. 8 130 5.74 32.44 861 8,254 1.4131 a (1 0 5.82 32.54 872 8,260 1.1 135 a-O-O, (95%); S.H.L., (5%) 5.8933.11 868 8,322 0 315 1 From Interpolated 40 viscosity.

a-olefin oligomer B contained 37.5% decene-ltrimer 2% decene-l tetramer.a-Olefin oligomer B contained 37.5% decene-l trimmer and 62.5% decene-ltetramer.

The following examples illustrate the advantage of using mixtures ofa-olefin oligomers and a synthetic hydrocarbon lubricant as the base oilin various compounded lubricants.

EXAMPLE 4 This example illustrates the advantage of using mix- Thephysical properties of the dialkylbenze (DAB-C 35 tures as a base oil ina hypoid gear oil. The gear oil cona-olefin oligomer A (a-O-O-A), anda-olefin oligomer B tained 6.5% of a commercial extreme pressureadditive and 93.5 weight percent of the base oil. The synthetichydrocarbon lubricant (S.H.L.) and oz-OlCfill oligomer TABLE IV Hypoidgear 011 Ratio: Percent S.H.L.: a-O-O 100:0 75:25 :50 25:75 0:100

Kinematic viscosity, cs. at-

40" F 10,328 9, 623 9, 331 9,060 9,809. Viscosity inde 111 113 123 126118. Pour point 65 65 -70. Storage stability tw 150 Pass Pass Pass PassFail, precipitated.

................... Pass Pass Pass Pass Fail, cloudy precipitated.

*Sample cloudy when value determined,

(a-O-O-B) and mixtures of the dialkylbenzene and each of the oligomersare shown in Table H below.

TABLE II A B C D DAB-C11, percent wt 0 70. 2 70. 2 e-O-O-A, percent wt-0 100 29. 8 0 d.-O-O'B, percent wt 0 0 0 29. 8 Viscosity indeq. 123 113111 Viscosity cs. at-

20. 65 14. 57 18. 39 23. 26 210 F 4.06 3. 43 3. 86 4.44 Percentdeviation from interpolated -40 vis 7. 5 5. 0 Pour point, F 75 75EXAMPLE 3 This example illustrates the improvement in -40 F.

viscosity of mixtures of linear mono-olefin oligomers (a-O-O) were thesame as in Example 3. The results are shown in Table IV.

EXAMPLE 5 TABLE V Gas turbine oil Ratio: Percent S.H.L.: Percent a-O-OKinematic viscosity, cs. at-

5.33 100 F 30. 34 F 949 40 F 10, 452 Viscosity index 120 P0111 point a F'765 Storage stability; two weeks at- 150 F Pass cipitated. 0 F PassPass Fail, cloudy... Fail, cloudy. precipitated Fail. cloudyprecipitated.

Not run, sample precipitated. 2 Sample cloudy when value determined.

EXAMPLE 6 This example is both illustrative and comparative in showingthe eifect of using mixtures as a base oil in an SE. engine oil. Use ofthe mixtures gave an improvement in viscosity index but no improvementin compatibility to the additive package. The engine oil contained 7.95weight percent of an additive combination which comprised an ashlessdispersant, an overbased magnesium sulfonate, a zinc dithiophosphateinhibitor, an overbased calcium phenate', and an ashless antioxidant and92.05 weight percent of the base oil. The synthetic" Hydrocarbonlubricant (S.H.L.) and a-oleiin oligomer '(m-O-O) were the same as inExamples 3, 4 and 5. The results are shown in Table VI.

TABLE VI S.E. engine oil Ratio: percent S.H.L.: percent a-O-O 100:075:25 50:50 25:75 0:100

Kinematic viscosity, cs. at-

210 F 6.02 6.25 6.46 6. 72 7. 07 100 F 30. B9 37. 47 38. 69 40. 11 45.29 0 F 1,209 1, 194 1, 191 1, 204 1, 229 30 F--- 6, 719 6,546 6. 405 6,340 6,447 Viscosity index- 119 127 130 135 126 Four point, F -65 60 6565 65 Storage stability; two weeks at- 150 Pass Pass Pass Pass Pass 0 FPass Pass Pass Pass 1 Sample cloudy when value determined.

EXAMPLE 7 ,decene;1 and contained at leas1; 5 0 weightprcent ofoligomers containing 24-60 carbon atoms.

The di-n-C -alkylbenzene had the following composition, as determined bymass spectrometer:

Percent Didecylbenhenes 96.4 Tridecylbenzenes 2.9 Miscellaneous alkylaromatics 0.6

The viscosity properties of the a-olefin oligomer (m-O-O) and the di-n-C-alkylbenzene (DAB-C and The data in Table VII shows that the measured40 F. viscosity is lower (which is an improvement) than the interpolatedviscosity for all of the mixtures and particularly is better for theblends containing 60, 40, and 20% of the oligomers. For example, on theblend containing 40% oligomers, the measured --40 F. viscosity was 4058cs., while the interpolated viscosity was 4900 cs. Thus the measuredviscosity showed a 17.1% deviation (an improvement) over the measuredviscosity.

While we have defined previously what is meant by interpolatedviscosity, the following amplification of the definition is provided.Referring to the table, it will be observed that ---4() F. viscositiesfor the pure materials were as follows: olefin oligomer-7949; di-C-alkylbenzone-2867.

The interpolated -40 F. viscosity for various mixtures of the twomaterials was determined by interpolation of these values using ordinarygraph paper, whereas logarithmic graph paper was used in the otherexamples herein. This diiference in type of graph paper does not make asubstantial difierence for the values described herein.

Thus, having described the invention in detail, it will be understood bythose skilled in the art that certain variations and modifications maybe made without departing from the spirit and scope of the invention asdefined herein and in the appended claim.

I claim:

1. A lubricant composition comprising a mixture of about 30 to about 85weight percent of a first component which is a linear mono-olefinoligomer, or mixtures thereof, and about 15 to about weight percent of asecond component which is a di-n-C -C alkylbenzene, a mixture of di-n-C-C alkylbenzenes or a synthetic hydrocarbon composition containing amajor amount of di-n- C -C alkylbenzenes, said linear mono-olefinoligomer, or mixtures thereof, containing at least 60 weight percentoligomers which contain 24 to 60 carbon atoms.

2. The lubricant-composition of claim 1 wherein said linear mono-olefinoligomers is prepared from a-olefins containing 8 to 12 carbon atoms.

3. The lubricant composition of claim 2 wherein the second component isa synthetic hydrocarbon composition various mix tures of the two areshown in Table VII. 50 having the following composition:

TABLE VII Ratio: percent a-O-O: percent DAB-Clo (by Weight) 100:0 90:10:20 60:40 40:60 20:80 10:90 0:100

Measured kinematic viscosity at- 210 F 5. 5. 00 5. 23 4. 65 4. 10 F---33. 25 30. 41 27. 90 24v 00 20. 57 40 F 7,949 7,269 6,485 4,997 4, 058Lineari y interpolated kinematic vlsocrty cs. at-

21 F 5. 65 5. 39 4. 88 4. 36 100 F 31. 5 29. 7 26. 1 22. 5 40 F 7,450 6,940 5,910 4, 900 Percent deviation from interpolated viscosity 210 F 0.93. 0 4. 7 4. 0 100 F 3. 5 6. 1 8.0 8. 4 40 F 2. 4 e. 5 15. 4 l7. 1Viscosity index 134 133 132 120 said synthetic hydrocarbon compositionbeing characterized as having a molecular weight of about 375 to about480, said fiialkyl-substituted tetrahydronaphthalenes being representedby the formula H t ll wherein R and R are straight-chain alkyl groupscontaining from 1 to about 13 carbon atoms each, with the sum of R and Rbeing from about 6 to about 14, and wherein R and R are straight-chainalkyl groups containing from about 1 to about 16 carbon atoms, with thesum of R and R being from about 9 to about 17.

4. The lubricant composition of claim 1 wherein the amount of said firstcomponent is about 50 to about 80 weight percent and the amount of saidsecond component is about 20 to about 50 weight percent.

5. The lubricant composition of claim 3 wherein the amount of said firstcomponent is about 50 to about 80 weight percent and the amount of saidsecond component is about 20 to about 50 weight percent.

6. A lubricant composition comprising a mixture of about 10 to about 90weight percent of a first component which is a linear mono-olefinoligomer, or mixtures thereof, said linear mono-olefin oligomercontaining at least 50 weight percent oligomer, which contain 24 to 60carbon atoms, and about 10 to about 90 weight percent of a secondcomponent which is a di-n-long-chain alkaryl compound, a mixture ofdi-n-long-chain alkaryl compounds, or a synthetic hydrocarboncomposition containing a major amount of di-n-long-chain alkarylcompounds, said lubricant composition being characterized in that:

(a) said di-n-long-chain alkaryl compound is represented by the formulawherein R and R are substantially straight-chain alkyl groups containingfrom 6 to 18 carbon atoms, with the sum of R and R being from about 20to about 28 carbon atoms and wherein A and A are hydrogen or a C or Calkyl group, and

(b) said synthetic hydrocarbon composition has the followingcomposition:

10 Component: Percent by weight Di-n-long-chain alkaryls 61-92-Trialkyl-substituted tetrahydronaphthalenes 5-30 Miscellaneous alkylaromatic compounds 15 said synthetic hydrocarbon composition beingcharacterized as having a molecular weight range of about 350 to about526, said di-n-long-chain alkaryls being represented by the formulawherein R and R are substantially straight-chain alkyl groups containingfrom 6 to 18 carbon atoms, with the sum of R and R being from about 20to about 28 carbon atoms, and wherein A and A are hydrogen or a C or Calkyl group, said trialkyl substituted tetrahydronaphthalenes beingrepresented by the formula wherein R and R are straight-chain alkylgroups containing from 1 to about 13 carbon atoms each, with the sum ofR and R being from about 6 to about 14, and wherein R and R arestraight-chain alkyl groups containing from about 1 to about 16 carbonatoms, with the sum of R and R being from about 9 to about 17.

7. The lubricant composition of claim 6 wherein said linear mono-olefinoligomer is prepared from a-olefins containing 6 to 16 carbon atoms.

8. The lubricant composition of claim 7 wherein the alkyl groups R and Rcontain from about 9 to about 15 carbon atoms.

9. The lubricant composition of claim 8 wherein R and R contain fromabout 10 to about 14 carbon atoms.

10. The lubricant composition of claim 9 wherein A and A are hydrogen.

11. A lubricant composition of claim 10 wherein said linear mono-olefinoligomer is prepared from a-olefins containing 8 to 12 carbon atoms.

References Cited UNITED STATES PATENTS 3,322,848 5/1967 Garwood et a1252-59 X 3,598,739 8/1971 Sias 25259 X 3,642,634 2/ 1972 Olund 25259 XWARREN H. CANNON, Primary Examiner

